• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.34-39
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• 2007

Condensing gas boiler units may make a big role for the reduction of energy consumption in heating industries. In order to decrease the energy consumption of a condensing gas boiler unit, the effective operations and controls of the system are necessary. In this study, mathematical models of a condensing gas boiler system were developed and programmed in order to predict dynamic behaviors of the system. These include dynamic models for a blower, a gas valve, a pump, a burner, a boiler heat exchanger, and a hot water heat exchanger. Control algorithms for the control of a gas valve, a blower, and a pump were also assumed. Simulation results showed good predictions of the dynamic phenomena of a boiler system. Therefore, the simulation program developed for this study may be effectively used for the development of control algorithms of the boiler system.

• Journal of Communications and Networks
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• v.6 no.2
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• pp.133-146
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• 2004

Recently, many active queue management (AQM) algorithms have been proposed to address the performance degradation. of end-to-end congestion control under tail-drop (TD) queue management at Internet routers. However, these AQM algorithms show performance improvement only for limited network environments, and are insensitive to dynamically changing network situations. In this paper, we propose an adaptive queue management algorithm, called PID-controller, that uses proportional-integral-derivative (PID) feedback control to remedy these weak-Dalles of existing AQM proposals. The PID-controller is able to detect and control congestion adaptively and proactively to dynamically changing network environments using incipient as well as current congestion indications. A simulation study over a wide range of IP traffic conditions shows that PID-controller outperforms other AQM algorithms such as Random Early Detection (RED) [3] and Proportional-Integral (PI) controller [9] in terms of queue length dynamics, packet loss rates, and link utilization.

• Proceedings of the KIEE Conference
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• summer
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• pp.1217-1219
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• 2004

This paper presents a modified PI control algorithm using pole placement for DC-to-DC converter of a magnetic levitation system(MAGLEV). The gains of the control algorithm were selected based on pole locations formulated from a prototype Bessel transfer function model. The design incorporate tradeoffs in DC-to-DC converter hardware parameters and pole locations. In order to confirm the superiority of the proposed pole selection and controller, simulation and experiment results are presented.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.760-763
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• 1996

This paper presents an algorithm for the contingency ranking in a power system. The method utilizes line outage distribution factors(LODF) which are established from DC load flow solutions. The LODF are formulated using changes in network power generations to simulate the outaged line from the network. To abtain better ranking. one can take a line loading of 60% over into account in the computation of PI. The proposed algorithm has been validated in tests on a 6-bus test system.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1086-1087
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• 2007

This paper presents a implementation of speed sensorless vector control algorithm of induction motor using MATLAB/SIMULINK. The proposed method utilize the combination of the voltage model based on stator equivalent model and the current model based on rotor equivalent model, which enables stable estimation of rotor flux. Estimated rotor speed, which is used to speed controller of induction motor, is based on estimated flux. The overall system consisted of speed controller with the most general PI controller, current controller, flux controller. Speed sensorless vector control algorithm is implemeted as block diagrams using MATLAB/SIMULINK. Realtime control is perform by dSPACE DS1104 control board and Real-Time-Interface(RTI).

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.693-696
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• 2003

Among many servo control systems in steel making plant, AGC system in hot rolling mill is very important to get a accurate strip thickness for good quality. AGC (Auto Gauge Control) system controls the roll gap to maintain the required thickness by using the variation of roll force and the measure of output thickness. In this paper, a simulator of AGC system which unifies both hydraulic servo control system and AGC algorithm is suggested. After proving the concurrence of algorithms between the simulator and real system, main actuator system is added. Instead of usual PI system used in present system, DOB control scheme is applied and shows the effect of disturbance attenuation well.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.4
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• pp.880-888
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• 2001

This paper presents a fault detection asnd isolation algorithm for highly reliable gantry crane system. The algorithm is constructed by multiple PI observer technique, and the magnitude of actuator fault can be estimated by using integrated estimated output error. Also, the complex actuator and /or sensor fault can be detected and isolated by monitoring the integrated error and the estimated state error. Considering the actuator and/or the sensor fault, we verify that these fault can be detected and isolated through simulation. Lastly, we show a simple reliable control method by using the detected fault signal and an added observer.

• The Journal of the Acoustical Society of Korea
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• v.24 no.7
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• pp.402-409
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• 2005

In this paper. we propose a coding method using a matching pursuit algorithm in a strongly periodic highband signal. Also. we propose an efficient quantizer for the estimated parameters : spectral magnitude and phase. Based on the error concealment principle and sinusoidal model. the MP algorithm requires the high-precision pitch period estimation. To estimate more accurate pitch period. the refined pitch obtained from lowband speech is used. which increases the efficiency of bit allocation. The spectral magnitude parameters are quantized by the method which is combined with MDCT (Modified Discrete Cosine Transform) and multi-stage structure. The spectral phase quantizer uses the $2{\pi}$ modular characteristic of phases and the weighted function by spectral magnitudes. To evaluate the efficiency of the proposed method. we applied it to analysis-by-synthesis system. Furthermore we suggest the possibillity of scalable wideband speech codecs based on band-split structure.

• Journal of Navigation and Port Research
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• v.32 no.5
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• pp.379-385
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• 2008

In this paper, we presents a scheme for the parameter estimation and optimal control scheme for apparatus of container crane system. For parameter estimation, first, we construct the open loop of the container crane system and estimate its parameters based on input-output data, a real-coded genetic algorithm(RCGA) and the model adjustment technique. The RCGA plays an important role in parameter estimation as an adaptive mechanism. For controller design, state feedback gain matrix is searched by another RCGA and the estimated model. The performance of the proposed methods are demonstrated through a set of simulation and experiments of the experimental apparatus.

• Journal of Advanced Navigation Technology
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• v.26 no.2
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• pp.119-124
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• 2022

The international gnss service (IGS) provides real-time service (RTS) orbit and clock correction applicable to the broadcast ephemeris of GNSS satellites. However, since the RTS correction cannot be received if the Internet connection is lost, the RTS correction should be predicted and used when a signal interruption occurs in order to perform stable precise point positioning (PPP). In this paper, PPP was performed by predicting orbit and clock correction using a long short-term memory (LSTM) algorithm in real-time during the signal loss. The prediction performance was analyzed by implementing the LSTM algorithm in RPI (raspberry pi), the processing speed of which is not high. Compared to the polynomial prediction model, LSTM showed excellent performance in long-term prediction.